1. Technical Field
The present invention relates to a correction information calculator, an image correction device, an image display system, and a correction information calculation method.
2. Related Art
In the related art, projectors are used for presentations in exhibitions, seminars, meetings, and the like, or home theater systems. Such projectors are also used for point-of-sale advertising. Since the use of projectors makes it easy to display an image on a larger screen than a direct-view type display device such as a display, projectors are highly convenient and can present the same image to many more people. In recent years, various developments have been made to cope with the market demands for high-quality projection images.
For example, when the central axis of the rays of image light emitted from a projector is projected in a direction intersecting the normal line of a projection surface (screen), or when a projection optical system of the projector has an aberration, a projection image projected onto the projection surface has a distortion. For example, an image that is to be displayed in a rectangular shape is projected as a distorted shape such as a trapezoidal shape or a rhombic shape.
As a method of correcting and eliminating this distortion, a method disclosed in JP-A-2004-363665 is known. In the method disclosed in JP-A-2004-363665, the coordinates of the four corners of a projection region of a projector are specified, and a distortion of an image is corrected so that the image is displayed within the range surrounded by the four corners, whereby a distortion-free projection image can be projected.
Moreover, the projection image projected by the projector depends on the number of pixels of an image forming element of the projector, such as a liquid-crystal light valve or a DMD (Digital Mirror Device). Therefore, in order to increase the resolution of the projection image projected by the projector, it is necessary to use an image forming element having a high resolution. However, such a high-resolution image forming element is expensive and is not suitable for general purposes.
In order to solve such a problem, a system that projects one image using a plurality of projectors has been developed (for example, see JP-A-2006-14356). In the system disclosed in JP-A-2006-14356, one image is divided into a plurality of projection images to be projected and displayed by a plurality of projectors, and the projection images are combined by superimposing the outer edges of the projection images of the respective projectors, whereby the projection images are projected as one image. In the following description, the image displayed by combining the projection images projected by the plurality of projectors is sometimes referred to as an “entire image.” Moreover, in the following description, the projection image projected from each of the plurality of projectors is sometimes referred to as a “partial image.”
Moreover, the maximum projectable range in which the projectable ranges of the respective projectors are put together is not necessarily rectangular. Therefore, in the system disclosed in JP-A-2006-14356, the projection images are captured by a digital camera, and a distortion of the projection region is corrected based on the captured images, so that a rectangular image can be displayed. For example, when the projection surface is a rolling screen, the projection image may have a distortion due to looseness or rippling of the screen. In the system disclosed in JP-A-2006-14356, such an image distortion is automatically corrected based on the captured images.
The use of such a system enables the resolution of the projection image to be increased by an amount corresponding to the number of used projectors even when the projectors have an image forming element having a normal resolution. Moreover, since the number of light sources also increases as the number of used projectors increases, if the size of the projection image is the same, it is possible to display a brighter image than the image projected by one projector. In addition, it is possible to display a distortion-free image.
However, in the system that automatically corrects the image distortion as disclosed in JP-A-2006-14356, the captured image itself may have a distortion when the central axis of the rays of light entering, for example, the digital camera is at a certain angle (shooting angle) with respect to the normal line of the projection surface. In that case, there is a difference in the distortion manner of the actual projection image and the captured image. Thus, correction is not made properly, and a distortion remains in the entire image (the projection region in which the entire image is projected).
In such a case, the user may try to make correction in order to eliminate the distortion of the entire image being projected. However, according to the existing correction methods, it is difficult to adjust the shape of the entire image while maintaining a state where the entire image is smoothly connected and displayed.
By combining the existing techniques, a correction method can be considered in which a distortion correction (first correction) is performed so as to eliminate a distortion of an entire image distorted with respect to image data to determine a region in which an ideal entire image is to be displayed, and then a position correction (second correction) is performed so as to divide corrected image data to create data of images (partial images) to be projected by respective projectors. However, since this correction method involves two correction operations on the image data, the image data are deteriorated greatly, leading to an image quality deterioration. Thus, the computation load increases, and the correction takes a lot of processing time. Therefore, it is unable to display videos without delay, for example.